Manganese is combustible, and finely dispersed particles can form explosive mixtures in air (NIOSH/IPCS 2003).

Data indicate that manganese exposure is associated with a range of neurobehavioral and neuropsychiatric changes, some of which may persist for long periods after occupational exposure ceases (ACGIH 2013).

One study found that six deaths from pneumonia in a Norwegian ferroalloy plant could be attributed to occupational exposures to manganese (Hobbesland et al. 1997). Another study looking at welders found three fatalities due to pneumonia that could be traced back to manganese exposure (Wergeland and Iversen 2001).

A study examining welders found that the only difference between welding-related Parkinsonism and idiopathic Parkinsonism is the age of onset. As a result, the authors concluded that welding could be a risk factor for developing Parkinson's Disease (Racette et al. 2001).

Based on the findings of neurobehavioral impairment by Roels et al. (1987, 1992), the LOAEL for derivation of the EPA RfC is 0.15 mg/m3, and the LOAEL(HEC) is 0.05 mg/m3.